This invention relates to the field of packaging, and, more particularly, to packaging by an integrated stretch wrap system which weighs, prices and wraps products in a stretchable wrapping film, and labels the wrapped products.
Stretch wrapping is a packaging technique especially for trayed products, wherein stretchable plastic film is wrapped in a stretched condition around a product to produce a tightly conforming and attractive package. With the availability of high speed automatic stretch wrapping equipment, this technique is gaining increased acceptance, particularly for food packaging.
One important application for automatic stretch wrapping machines is in the packaging of fresh food products in individual supermarkets. The stretch wrapped fresh food products are very attractive, and the wrapping film also provides adequate breathing to maintain the wrapped food in a fresh state.
For supermarket application, however, stretch wrapping machines must be capable of wrapping products which vary considerably in size and weight over very short runs. An example of this is in the wrapping of fresh meat. When beef is being wrapped at a supermarket, for example, there may be 10 or 20 tenderloin steaks, followed by 10 or 20 T-bone steaks, followed by 10 or 20 trays of hamburger meat or various other cuts of beef. A11 of the pieces in any given run of these products may differ somewhat from one another in size and weight, and the difference is even greater from one short run of one cut to the next short run of another cut.
Moreover, since meat is a relatively expensive commodity, and it is generally sold on a per pound basis, it is essential that each individual package be accurately weighed, priced and labeled. Also, it is desirable that the label be consistently applied to the same general location of the package, regardless of variations in package size, so that the packaged goods may be conveniently displayed, with the price visible or readily ascertainable, and the goods quickly processed at the check-out counter. Further, the equipment must not only be accurate and adaptable to a variety of rapidly changing sizes and weights; it must also be relatively small, because of space limitations, simple to operate by unskilled operators, and relatively inexpensive.
These requirements are in contrast to the requirements for machines in central packaging locations, where space is generally not as critical, where the operators may be trained and experienced machine operators, where the cost is not so critical since the machine may run continuously through all working hours, and where one product may be wrapped continuously for hours or days, so that an appreciable set-up time for changing the machine to accomodate another product forms only a small fraction of the total operating time.
Because of the severe constraints on supermarket wrapping machines, weighing and labeling are generally performed separate from the wrapping, on a computerized electronic scale with a label printing and applying attachment. These scales require a manual input by a machine operator identifying the type of commodity, the unit price per weight, and the tare weight of the packaging material. Each product is typically wrapped in a wrapping machine and then transferred to the electronic scale. After weighing the wrapped product, the scale unit subtracts the tare of the wrapping material, to determine the net weight, and then multiplies the net weight by the unit price to determine the selling price. The price is printed on a label, along with the type of product, net weight, and unit price per pound, and the label is applied to the previously wrapped product. It may also be required to prepare and apply an additional label bearing the universal product code (UPC) for the particular wrapped product.
When the volume of packages being handled is low, the system described can be manually fed by an operator, handling each package individually in both the wrapping and weighing apparatus. However, when the volume of packages is high, such as is generally the case when the product is wrapped by automatic equipment, the separate wrapping and weighing apparatus must be converted to a compatible automatic system in which the weighing apparatus can accept and process the output of the wrapping apparatus. This automation is accomplished, in present supermarket equipment, by combining the computerized scale and labeling unit, and the wrapping machine, with an automatic indexing and orienting conveyor system. In these integrated systems, the conveyor system accepts packages from the discharge of the automatic wrapper, gates and indexes them at predetermined intervals, aligns them for proper presentation to the weighing station, transfers them in sequence to the weighing station, where they are weighed in turn, transfers them to an alignment station where they are aligned for the label applicator, transfers them to the label applicator station where the labels are applied, and finally, discharges the labeled packages.
There are several disadvantages to this system. First, the indexing and orienting systems are quite expensive, so that the complete system is very expensive. Second, the system is bulky, and requires an excessive amount of floor space. Furthermore, because of the size of the system, there is a considerable distance between the product input and controls of the wrapping machine and the controls of the scale, so that two operators are required, or one operator must move from one location to another for product changes. Indeed, since product changes are frequent, and a manual input to the scale control is required for every product change, either one operator is used to operate the system at a greatly reduced output rate, or two operators are required. These disadvantages and others are overcome by the present invention.
It is an object of the present invention to provide a relatively simple to operate, small, inexpensive and accurate system, operable by a single operator, to rapidly weigh, wrap, price and label numerous products of widely varying sizes, weights, and unit prices.